Measurement gap enhancements for BL/CE UEs

ABSTRACT

Aspects of the present disclosure provide techniques and apparatus for wireless communication. In one aspect, a method is provided which may be performed by a wireless device such as a user equipment (UE). The method generally includes determining a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap, and adjusting the measurement gap based on at least one criterion.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application for patent claims the benefit of U.S. Provisional Application Ser. No. 62/584,676, filed on Nov. 10, 2017, which is expressly incorporated by reference herein in its entirety.

BACKGROUND Field of the Disclosure

Certain aspects of the present disclosure generally relate to wireless communications and, more particularly, to measurement gap enhancements for BL (bandwidth reduced low complexity)/CE (coverage enhancement) UEs (user equipments).

Description of Related Art

Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE)/LTE-Advanced (LTE-A) systems and orthogonal frequency division multiple access (OFDMA) systems.

Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations (BSs) via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the BSs to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the BSs. This communication link may be established via a single-input single-output, multiple-input single-output or a multiple-input multiple-output (MIMO) system.

A wireless communication network may include a number of BSs that can support communication for a number of wireless devices. Wireless devices may include user equipments (UEs). Machine type communications (MTC) may refer to communication involving at least one remote device on at least one end of the communication and may include forms of data communication which involve one or more entities that do not necessarily need human interaction. MTC UEs may include UEs that are capable of MTC communications with MTC servers and/or other MTC devices through Public Land Mobile Networks (PLMN), for example. Wireless devices may include Internet-of-Things (IoT) devices (e.g., narrowband IoT (NB-IoT) devices). IoT may refer to a network of physical objects, devices, or “things”. IoT devices may be embedded with, for example, electronics, software, or sensors and may have network connectivity, which enable these devices to collect and exchange data.

Some next generation, NR, or 5G networks may include a number of base stations, each simultaneously supporting communication for multiple communication devices, such as UEs. In LTE or LTE-A network, a set of one or more BSs may define an e NodeB (eNB). In other examples (e.g., in a next generation or 5G network), a wireless multiple access communication system may include a number of distributed units (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (e.g., CU, central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more distributed units (DUs), in communication with a CU, may define an access node (e.g., AN, a new radio base station (NR BS), a NR NB, a network node, a gNB, a 5G BS, an access point (AP), etc.). A BS or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a BS or to a UE) and uplink channels (e.g., for transmissions from a UE to a BS or DU).

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. NR (e.g., 5G radio access) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. NR is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on the downlink (DL) and on the uplink (UL) as well as support beamforming, MIMO antenna technology, and carrier aggregation.

However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE, MTC, IoT, and NR (new radio) technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

The systems, methods, and devices of the disclosure each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled “DETAILED DESCRIPTION” one will understand how the features of this disclosure provide advantages that include improved communications between access points and stations in a wireless network.

Certain aspects of the present disclosure generally relate to measurement gap enhancements for BL/CE UEs.

Certain aspects of the present disclosure provide a method, performed by a wireless device, such as a user equipment (UE). The method generally includes determining a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap, and adjusting the measurement gap based on at least one criterion.

Certain aspects of the present disclosure provide an apparatus. The apparatus generally includes at least one processor configured to: determine a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap, and adjust the measurement gap based on at least one criterion; and a memory coupled to the at least one processor.

Certain aspects of the present disclosure provide an apparatus. The apparatus generally includes means for determining a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap, and means for adjusting the measurement gap based on at least one criterion.

Certain aspects of the present disclosure provide a computer-readable medium. The computer-readable medium generally includes code, the code, when executed by at least one processor, causes the at least one processor to: determine a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap, and adjust the measurement gap based on at least one criterion.

Numerous other aspects are provided including methods, apparatus, systems, computer program products, computer-readable medium, and processing systems. To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an example of a wireless communication network, in accordance with certain aspects of the present disclosure.

FIG. 2 shows a block diagram conceptually illustrating an example of a base station (BS) in communication with a user equipment (UE) in a wireless communications network, in accordance with certain aspects of the present disclosure.

FIG. 3 is a block diagram conceptually illustrating an example of a frame structure in a wireless communications network, in accordance with certain aspects of the present disclosure.

FIG. 4 is a block diagram conceptually illustrating two exemplary subframe formats with the normal cyclic prefix, in accordance with certain aspects of the present disclosure.

FIG. 5 illustrates an exemplary subframe configuration for enhanced/evolved machine type communications (eMTC), in accordance with certain aspects of the present disclosure.

FIG. 6 illustrates an example deployment of narrowband Internet-of-Things (NB-IoT), in accordance with certain aspects of the present disclosure.

FIG. 7 illustrates an example logical architecture of a distributed radio access network (RAN), in accordance with certain aspects of the present disclosure.

FIG. 8 illustrates an example physical architecture of a distributed RAN, in accordance with certain aspects of the present disclosure.

FIG. 9 is a diagram illustrating an example of a downlink (DL)-centric subframe, in accordance with certain aspects of the present disclosure.

FIG. 10 is a diagram illustrating an example of an uplink (UL)-centric subframe, in accordance with certain aspects of the present disclosure.

FIG. 11 provides an illustration of dynamic gap length extension.

FIG. 12 illustrates one option for dynamic gap length extension.

FIG. 13 illustrates another option for dynamic gap length extension.

FIG. 14A illustrates an example processing delay for RRC procedures. FIG. 14B illustrates one row of a table on RRC procedure delay.

FIG. 15 is a flow diagram illustrating example operations for a user equipment, in accordance with certain aspects of the present disclosure.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized on other aspects without specific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide techniques for measurement gap enhancements. The techniques described herein may be used for various wireless communication networks such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network may implement a radio technology such as universal terrestrial radio access (UTRA), cdma2000, etc. UTRA includes wideband CDMA (WCDMA), time division synchronous CDMA (TD-SCDMA), and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as global system for mobile communications (GSM). An OFDMA network may implement a radio technology such as evolved UTRA (E-UTRA), ultra mobile broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part of universal mobile telecommunication system (UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A), in both frequency division duplex (FDD) and time division duplex (TDD), are new releases of UMTS that use E-UTRA, which employs OFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). NR (e.g., 5G radio access) is an example of an emerging telecommunication standard. NR is a set of enhancements to the LTE mobile standard promulgated by 3GPP. The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies. For clarity, certain aspects of the techniques are described below for LTE/LTE-Advanced, and LTE/LTE-Advanced (LTE-A) terminology is used in much of the description below. LTE and LTE-A are referred to generally as LTE. Depending on the context, “channel” may refer to the channel on which signaling/data/information is transmitted or received, or to the signaling/data/information that is transmitted or received on the channel.

It is noted that while aspects may be described herein using terminology commonly associated with 3G and/or 4G wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems, such as 5G and later.

Example Wireless Communications Network

FIG. 1 illustrates an example wireless communication network 100, in which aspects of the present disclosure may be practiced. For example, techniques presented herein may be used for measurement gap enhancement in wireless communication network 100, which may be an LTE or later network that includes narrowband Internet-of-things (NB-IoT) and/or enhanced/evolved machine type communications (eMTC) devices. Wireless communication network 100 may include base stations (BSs) 110 and user equipment (UEs) 120. In aspects, a BS 110 can determine at least one narrowband region of a wideband region for communication with a UE 120. UE 120, which may be a low cost device, such a NB-IoT device or an eMTC UE, can determine the narrowband region and receive, send, monitor, or decode information on the narrowband region for communication with BS 110.

Wireless communication network 100 may be a long term evolution (LTE) network or some other wireless network, such as a new radio (NR) or 5G network. Wireless communication network 100 may include a number of BSs 110 and other network entities. A BS is an entity that communicates with UEs and may also be referred to as a NR BS, a Node B (NB), an evolved/enhanced NB (eNB), a 5G NB, a gNB, an access point (AP), a transmission reception point (TRP), etc. Each BS may provide communication coverage for a particular geographic area. In 3GPP, the term “cell” can refer to a coverage area of a BS and/or a BS subsystem serving this coverage area, depending on the context in which the term is used.

A BS may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs having association with the femto cell (e.g., UEs in a closed subscriber group (CSG)). A BS for a macro cell may be referred to as a macro BS. A BS for a pico cell may be referred to as a pico BS. A BS for a femto cell may be referred to as a femto BS or a home BS. In the example shown in FIG. 1, BS 110 a may be a macro BS for a macro cell 102 a, BS 110 b may be a pico BS for a pico cell 102 b, and BS 110 c may be a femto BS for a femto cell 102 c. A BS may support one or multiple (e.g., three) cells. The terms “base station” and “cell” may be used interchangeably herein.

Wireless communication network 100 may also include relay stations. A relay station is an entity that can receive a transmission of data from an upstream station (e.g., BS 110 or UE 120) and send a transmission of the data to a downstream station (e.g., UE 120 or BS 110). A relay station may also be a UE that can relay transmissions for other UEs. In the example shown in FIG. 1, relay station 110 d may communicate with macro BS 110 a and UE 120 d in order to facilitate communication between BS 110 a and UE 120 d. A relay station may also be referred to as a relay BS, a relay, etc.

Wireless communication network 100 may be a heterogeneous network that includes BSs of different types, e.g., macro BSs, pico BSs, femto BSs, relay BSs, etc. These different types of BSs may have different transmit power levels, different coverage areas, and different impact on interference in wireless communication network 100. For example, macro BSs may have a high transmit power level (e.g., 5 to 40 Watts) whereas pico BSs, femto BSs, and relay BSs may have lower transmit power levels (e.g., 0.1 to 2 Watts).

Network controller 130 may couple to a set of BSs and may provide coordination and control for these BSs. Network controller 130 may communicate with the BSs via a backhaul. The BSs may also communicate with one another, e.g., directly or indirectly via a wireless or wireline backhaul.

UEs 120 (e.g., UE 120 a, UE 120 b, UE 120 c) may be dispersed throughout wireless communication network 100, and each UE may be stationary or mobile. A UE may also be referred to as an access terminal, a terminal, a mobile station, a subscriber unit, a station, a Customer Premises Equipment (CPE), etc. A UE may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a drone, a robot/robotic device, a netbook, a smartbook, an ultrabook, a medical device, medical equipment, a healthcare device, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, virtual reality goggles, a smart wristband, and/or smart jewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainment device (e.g., a music device, a video device, a gaming device, a satellite radio, etc.), industrial manufacturing equipment, a navigation/positioning device (e.g., GNSS (global navigation satellite system) devices based on, for example, GPS (global positioning system), Beidou, GLONASS, Galileo, terrestrial-based devices, etc.), or any other suitable device configured to communicate via a wireless or wired medium. Some UEs may be implemented as IoT (Internet of things) UEs. IoT UEs include, for example, robots/robotic devices, drones, remote devices, sensors, meters, monitors, cameras, location tags, etc., that may communicate with a BS, another device (e.g., remote device), or some other entity. IoT UEs may include MTC/eMTC UEs, NB-IoT UEs, as well as other types of UEs. A wireless node may provide, for example, connectivity for or to a network (e.g., a wide area network such as Internet or a cellular network) via a wired or wireless communication link.

One or more UEs 120 in the wireless communication network 100 (e.g., an LTE network) may be a narrowband bandwidth UE. As used herein, devices with limited communication resources, e.g. smaller bandwidth, may be referred to generally as narrowband (NB) UEs or bandwidth reduced low complexity (BL) UEs. In one example, a limited bandwidth may be 1.4 MHz. In another example, a limited bandwidth may be 5 MHz. Similarly, legacy devices, such as legacy and/or advanced UEs (e.g., in LTE) may be referred to generally as wideband UEs. Generally, wideband UEs are capable of operating on a larger amount of bandwidth than narrowband UEs.

In FIG. 1, a solid line with double arrows indicates desired transmissions between a UE and a serving BS, which is a BS designated to serve the UE on the downlink and/or uplink. A dashed line with double arrows indicates potentially interfering transmissions between a UE and a BS.

In general, any number of wireless networks may be deployed in a given geographic area. Each wireless network may support a particular radio access technology (RAT) and may operate on one or more frequencies. A RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a frequency channel, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs. In some cases, NR or 5G RAT networks may be deployed.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a BS 110) allocates resources for communication among some or all devices and equipment within its service area or cell. The scheduling entity may be responsible for scheduling, assigning, reconfiguring, and releasing resources for one or more subordinate entities. For scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. BSs 110 are not the only entities that may function as a scheduling entity. In some examples, UE 120 may function as a scheduling entity, scheduling resources for one or more subordinate entities (e.g., one or more other UEs 120). In this example, the UE is functioning as a scheduling entity, and other UEs utilize resources scheduled by the UE for wireless communication. A UE may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs may optionally communicate directly with one another in addition to communicating with the scheduling entity.

Thus, in a wireless communication network with a scheduled access to time-frequency resources and having a cellular configuration, a P2P configuration, and a mesh configuration, a scheduling entity and one or more subordinate entities may communicate utilizing the scheduled resources.

FIG. 2 shows a block diagram of a design of BS 110 and UE 120, which may be one of the BSs 110 and one of the UEs 120 in FIG. 1. BS 110 may be equipped with T antennas 234 a through 234 t, and UE 120 may be equipped with R antennas 252 a through 252 r, where in general T≥1 and R≥1.

At BS 110, transmit processor 220 may receive data from a data source 212 for one or more UEs, select one or more modulation and coding schemes (MCS) for each UE based on channel quality indicators (CQIs) received from the UE, process (e.g., encode and modulate) the data for each UE based on the MCS(s) selected for the UE, and provide data symbols for all UEs. Transmit processor 220 may also process system information (e.g., for static resource partitioning information (SRPI), etc.) and control information (e.g., CQI requests, grants, upper layer signaling, etc.) and provide overhead symbols and control symbols. Processor 220 may also generate reference symbols for reference signals (e.g., the cell-specific reference signal (CRS)) and synchronization signals (e.g., the primary synchronization signal (PSS) and the secondary synchronization signal (SSS)). Transmit (TX) multiple-input multiple-output (MIMO) processor 230 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, the overhead symbols, and/or the reference symbols, if applicable, and may provide T output symbol streams to T modulators (MODs) 232 a through 232 t. Each modulator 232 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator 232 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. T downlink signals from modulators 232 a through 232 t may be transmitted via T antennas 234 a through 234 t, respectively.

At UE 120, antennas 252 a through 252 r may receive the downlink signals from base station 110 and/or other BSs and may provide received signals to demodulators (DEMODs) 254 a through 254 r, respectively. Each demodulator 254 may condition (e.g., filter, amplify, downconvert, and digitize) its received signal to obtain input samples. Each demodulator 254 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. MIMO detector 256 may obtain received symbols from all R demodulators 254 a through 254 r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. Receive processor 258 may process (e.g., demodulate and decode) the detected symbols, provide decoded data for UE 120 to data sink 260, and provide decoded control information and system information to controller/processor 280. A channel processor may determine reference signal received power (RSRP), received signal strength indicator (RSSI), reference signal received quality (RSRQ), CQI, etc.

On the uplink, at UE 120, transmit processor 264 may receive and process data from data source 262 and control information (e.g., for reports comprising RSRP, RSSI, RSRQ, CQI, etc.) from controller/processor 280. Processor 264 may also generate reference symbols for one or more reference signals. The symbols from transmit processor 264 may be precoded by TX MIMO processor 266 if applicable, further processed by modulators 254 a through 254 r (e.g., for SC-FDM, OFDM, etc.), and transmitted to BS 110. At BS 110, the uplink signals from UE 120 and other UEs may be received by antennas 234, processed by demodulators 232, detected by MIMO detector 236 if applicable, and further processed by receive processor 238 to obtain decoded data and control information sent by UE 120. Processor 238 may provide the decoded data to data sink 239 and the decoded control information to controller/processor 240. BS 110 may include communication unit 244 and communicate to network controller 130 via communication unit 244. Network controller 130 may include communication unit 294, controller/processor 290, and memory 292.

Controllers/processors 240 and 280 may direct the operation at BS 110 and UE 120, respectively, to perform techniques presented herein. For example, processor 240 and/or other processors and modules at BS 110, and processor 280 and/or other processors and modules at UE 120, may perform or direct operations of BS 110 and UE 120, respectively. For example, controller/processor 280 and/or other controllers/processors and modules at UE 120 may perform or direct operations 1500 shown in FIG. 15. Memories 242 and 282 may store data and program codes for BS 110 and UE 120, respectively. Scheduler 246 may schedule UEs for data transmission on the downlink and/or uplink.

FIG. 3 shows an exemplary frame structure 300 for frequency division duplexing (FDD) in a wireless communication system (e.g., such as wireless communication network 100). The transmission timeline for each of the downlink and uplink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms)) and may be partitioned into 10 subframes with indices of 0 through 9. Each subframe may include two slots. Each radio frame may thus include 20 slots with indices of 0 through 19. Each slot may include L symbol periods, for example, seven symbol periods for a normal cyclic prefix (as shown in FIG. 3) or six symbol periods for an extended cyclic prefix. The 2L symbol periods in each subframe may be assigned indices of 0 through 2L−1.

In certain wireless communication systems (e.g., LTE), a BS (e.g., such as a BS 110) may transmit a PSS and a SSS on the downlink in the center of the system bandwidth for each cell supported by the BS. The PSS and SSS may be transmitted in symbol periods 6 and 5, respectively, in subframes 0 and 5 of each radio frame with the normal cyclic prefix, as shown in FIG. 3. The PSS and SSS may be used by UEs (e.g., such as UEs 120) for cell search and acquisition. The BS may transmit a CRS across the system bandwidth for each cell supported by the BS. The CRS may be transmitted in certain symbol periods of each subframe and may be used by the UEs to perform channel estimation, channel quality measurement, and/or other functions. The BS may also transmit a physical broadcast channel (PBCH) in symbol periods 0 to 3 in slot 1 of certain radio frames. The PBCH may carry some system information. The BS may transmit other system information such as system information blocks (SIBs) on a physical downlink shared channel (PDSCH) in certain subframes. The BS may transmit control information/data on a physical downlink control channel (PDCCH) in the first B symbol periods of a subframe, where B may be configurable for each subframe. The BS may transmit traffic data and/or other data on the PDSCH in the remaining symbol periods of each subframe.

In certain systems (e.g., such as NR or 5G systems), a BS may transmit these or other signals in these locations or in different locations of the subframe.

FIG. 4 shows two exemplary subframe formats 410 and 420 with the normal cyclic prefix. The available time frequency resources may be partitioned into resource blocks (RBs). Each RB may cover 12 subcarriers in one slot and may include a number of resource elements (REs). Each RE may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value.

Subframe format 410 may be used for two antennas. A CRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7 and 11. A reference signal is a signal that is known a priori by a transmitter and a receiver and may also be referred to as pilot. A CRS is a reference signal that is specific for a cell, e.g., generated based on a cell identity (ID). In FIG. 4, for a given RE with label Ra, a modulation symbol may be transmitted on that RE from antenna a, and no modulation symbols may be transmitted on that RE from other antennas. Subframe format 420 may be used with four antennas. A CRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7 and 11 and from antennas 2 and 3 in symbol periods 1 and 8. For both subframe formats 410 and 420, a CRS may be transmitted on evenly spaced subcarriers, which may be determined based on cell ID. CRSs may be transmitted on the same or different subcarriers, depending on their cell IDs. For both subframe formats 410 and 420, REs not used for the CRS may be used to transmit data (e.g., traffic data, control data, and/or other data).

The PSS, SSS, CRS and PBCH in LTE are described in 3GPP TS 36.211, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation,” which is publicly available.

An interlace structure may be used for each of the downlink and uplink for FDD in LTE. For example, Q interlaces with indices of 0 through Q−1 may be defined, where Q may be equal to 4, 6, 8, 10, or some other value. Each interlace may include subframes that are spaced apart by Q frames. In particular, interlace q may include subframes q, q+Q, q+2Q, etc., where q∈{0, . . . , Q−1}.

The wireless network may support hybrid automatic retransmission request (HARQ) for data transmission on the downlink and uplink. For HARQ, a transmitter (e.g., a BS) may send one or more transmissions of a packet until the packet is decoded correctly by a receiver (e.g., a UE) or some other termination condition is encountered. For synchronous HARQ, all transmissions of the packet may be sent in subframes of a single interlace. For asynchronous HARQ, each transmission of the packet may be sent in any subframe.

A UE may be located within the coverage of multiple BS. One of these BSs may be selected to serve the UE. The serving BS may be selected based on various criteria such as received signal strength, received signal quality, pathloss, etc. Received signal quality may be quantified by a signal-to-noise-and-interference ratio (SINR), or a RSRQ, or some other metric. The UE may operate in a dominant interference scenario in which the UE may observe high interference from one or more interfering BS.

The wireless communication network may support a 180 kHz deployment for narrowband operation (e.g., NB-IoT) with different deployment modes. In one example, narrowband operations may be deployed in-band, for example, using RBs within a wider system bandwidth. In one case, narrowband operations may use one RB within the wider system bandwidth of an existing network (e.g., such as an LTE network). In this case, the 180 kHz bandwidth for the RB may have to be aligned with a wideband RB. In one example, narrowband operations may be deployed in the unused RBs within a carrier guard-band (e.g., LTE). In this deployment, the 180 kHz RB within the guard band may be aligned with a 15 kHz tone grid of wideband LTE, for example, in order to use the same Fast Fourier Transform (FFT) and/or reduce interference in-band legacy LTE communications.

Example Narrowband Communications

The focus of traditional LTE design (e.g., for legacy “non MTC” devices) is on the improvement of spectral efficiency, ubiquitous coverage, and enhanced quality of service (QoS) support. Current LTE system downlink (DL) and uplink (UL) link budgets are designed for coverage of high end devices, such as state-of-the-art smartphones and tablets, which may support a relatively large DL and UL link budget.

However, as described above, one or more UEs in the wireless communication network (e.g., wireless communication network 100) may be devices that have limited communication resources, such as narrowband UEs, as compared to other (wideband) devices in the wireless communication network. For narrowband UEs, various requirements may be relaxed as only a limited amount of information may need to be exchanged. For example, maximum bandwidth may be reduced (relative to wideband UEs), a single receive radio frequency (RF) chain may be used, peak rate may be reduced (e.g., a maximum of 100 bits for a transport block size), transmit power may be reduced, Rank 1 transmission may be used, and half duplex operation may be performed.

In some cases, if half-duplex operation is performed, MTC UEs may have a relaxed switching time to transition from transmitting to receiving (or receiving to transmitting). For example, the switching time may be relaxed from 20 μs for regular UEs to 1 ms for MTC UEs. Release 12 MTC UEs may still monitor downlink (DL) control channels in the same way as regular UEs, for example, monitoring for wideband control channels in the first few symbols (e.g., PDCCH) as well as narrowband control channels occupying a relatively narrowband, but spanning a length of a subframe (e.g., enhanced PDCCH or ePDCCH).

Certain standards (e.g., LTE Release 13) may introduce support for various additional MTC enhancements, referred to herein as enhanced MTC (or eMTC). For example, eMTC may provide MTC UEs with coverage enhancements up to 15 dB.

As illustrated in the subframe structure 500 of FIG. 5, eMTC UEs can support narrowband operation while operating in a wider system bandwidth (e.g., 1.4/3/5/10/15/20 MHz). In the example illustrated in FIG. 5, a conventional legacy control region 510 may span system bandwidth of a first few symbols, while a narrowband region 530 of the system bandwidth (spanning a narrow portion of a data region 520) may be reserved for an MTC physical downlink control channel (referred to herein as an M-PDCCH) and for an MTC physical downlink shared channel (referred to herein as an M-PDSCH). In some cases, an MTC UE monitoring the narrowband region may operate at 1.4 MHz or 6 resource blocks (RBs).

However, as noted above, eMTC UEs may be able to operate in a cell with a bandwidth larger than 6 RBs. Within this larger bandwidth, each eMTC UE may still operate (e.g., monitor/receive/transmit) while abiding by a 6-physical resource block (PRB) constraint. In some cases, different eMTC UEs may be served by different narrowband regions (e.g., with each spanning 6-PRB blocks). As the system bandwidth may span from 1.4 to 20 MHz, or from 6 to 100 RBs, multiple narrowband regions may exist within the larger bandwidth. An eMTC UE may also switch or hop between multiple narrowband regions in order to reduce interference.

Example Narrowband Internet-of-Things

The Internet-of-Things (IoT) may refer to a network of physical objects, devices, or “things”. IoT devices may be embedded with, for example, electronics, software, or sensors and may have network connectivity, which enable these devices to collect and exchange data. IoT devices may be sensed and controlled remotely across existing network infrastructure, creating opportunities for more direct integration between the physical world and computer-based systems and resulting in improved efficiency, accuracy, and economic benefit. Systems that include IoT devices augmented with sensors and actuators may be referred to cyber-physical systems. Cyber-physical systems may include technologies such as smart grids, smart homes, intelligent transportation, and/or smart cities. Each “thing” (e.g., IoT device) may be uniquely identifiable through its embedded computing system may be able to interoperate within existing infrastructure, such as Internet infrastructure.

NB-IoT may refer to a narrowband (NB) radio technology specially designed for the IoT. NB-IoT may focus on indoor coverage, low cost, long battery life, and large number of devices. To reduce the complexity of UEs, NB-IoT may allow for narrowband deployments utilizing one PRB (e.g., 180 kHz+20 kHz guard band). NB-IoT deployments may utilize higher layer components of certain systems (e.g., LTE) and hardware to allow for reduced fragmentation and cross compatibility with, for example, NB-LTE/NB-IoT and/or eMTC.

FIG. 6 illustrates an example deployment 600 of NB-IoT, according to certain aspects of the present disclosure. Three NB-IoT deployment configurations include in-band, guard-band, and standalone. For the in-band deployment configuration, NB-IoT may coexist with a legacy system (e.g., GSM, WCDMA, and/or LTE system(s)) deployed in the same frequency band. For example, the wideband LTE channel may be deployed in various bandwidths between 1.4 MHz to 20 MHz. As shown in FIG. 6, a dedicated RB 602 within that bandwidth may be available for use by NB-IoT and/or the RBs 1204 may be dynamically allocated for NB-IoT. As shown in FIG. 6, in an in-band deployment, one RB, or 200 kHz, of a wideband channel (e.g., LTE) may be used for NB-IoT.

Certain systems (e.g., LTE) may include unused portions of the radio spectrum between carriers to guard against interference between adjacent carriers. In some deployments, NB-IoT may be deployed in a guard band 606 of the wideband channel.

In other deployments, NB-IoT may be deployed standalone (not shown). In a standalone deployment, for example, one 200 MHz carrier may be utilized to carry NB-IoT traffic and GSM spectrum may be reused.

Deployments of NB-IoT may include synchronization signals such as PSS for frequency and timing synchronization and SSS to convey system information. For NB-IoT operations, PSS/SSS timing boundaries may be extended as compared to the existing PSS/SSS frame boundaries in legacy systems (e.g., LTE), for example, from 10 ms to 40 ms. Based on the timing boundary, a UE is able to receive a PBCH transmission, which may be transmitted in subframe 0 of a radio frame.

Example NR/5G RAN Architecture

New radio (NR) may refer to radios configured to operate according to a new air interface (e.g., other than Orthogonal Frequency Divisional Multiple Access (OFDMA)-based air interfaces) or fixed transport layer (e.g., other than Internet Protocol (IP)). NR may utilize OFDM with a CP on the uplink and downlink and include support for half-duplex operation using TDD. NR may include Enhanced Mobile Broadband (eMBB) service targeting wide bandwidth (e.g. 80 MHz beyond), millimeter wave (mmW) targeting high carrier frequency (e.g. 60 GHz), massive MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra reliable low latency communications (URLLC) service.

A single component carrier (CC) bandwidth of 100 MHZ may be supported. NR RBs may span 12 sub-carriers with a sub-carrier bandwidth of 75 kHz over a 0.1 ms duration. Each radio frame may consist of 50 subframes with a length of 10 ms. Consequently, each subframe may have a length of 0.2 ms. Each subframe may indicate a link direction (e.g., DL or UL) for data transmission and the link direction for each subframe may be dynamically switched. Each subframe may include DL/UL data as well as DL/UL control data. UL and DL subframes for NR may be as described in more detail below with respect to FIGS. 9 and 10.

Beamforming may be supported and beam direction may be dynamically configured. MIMO transmissions with precoding may also be supported. MIMO configurations in the DL may support up to 8 transmit antennas with multi-layer DL transmissions up to 8 streams and up to 2 streams per UE. Multi-layer transmissions with up to 2 streams per UE may be supported. Aggregation of multiple cells may be supported with up to 8 serving cells. Alternatively, NR may support a different air interface, other than an OFDM-based interface. NR networks may include entities such central units (CUs) or distributed units (DUs).

The NR RAN may include a CU and DUs. A NR BS (e.g., a NB, an eNB, a gNB, a 5G NB, a TRP, an AP, etc.) may correspond to one or multiple BSs. NR cells can be configured as access cells (ACells) or data only cells (DCells). For example, the RAN (e.g., a CU or DU) can configure the cells. DCells may be cells used for carrier aggregation or dual connectivity, but not used for initial access, cell selection/reselection, or handover. In some cases DCells may not transmit synchronization signals—in some case cases DCells may transmit synchronization signals.

FIG. 7 illustrates an example logical architecture 700 of a distributed RAN, according to aspects of the present disclosure. 5G access node 706 may include access node controller (ANC) 702. ANC 702 may be a CU of the distributed RAN. The backhaul interface to the next generation core network (NG-CN) 704 may terminate at ANC 702. The backhaul interface to neighboring next generation access nodes (NG-ANs) 710 may terminate at ANC 702. ANC 702 may include one or more TRPs 708. As described above, TRP may be used interchangeably with “cell”, BS, NR BS, NB, eNB, 5G NB, gNB, AP, etc.

TRPs 708 may comprise a DU. TRPs 708 may be connected to one ANC (e.g., ANC 702) or more than one ANC (not illustrated). For example, for RAN sharing, radio as a service (RaaS), and service specific AND deployments, TRP 708 may be connected to more than one ANC. TRP 708 may include one or more antenna ports. TRPs 708 may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE.

Logical architecture 700 may be used to illustrate fronthaul definition. The architecture may be defined that support fronthauling solutions across different deployment types. For example, logical architecture 700 may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter). Logical architecture 700 may share features and/or components with LTE. According to aspects, NG-AN 710 may support dual connectivity with NR. NG-AN 710 may share a common fronthaul for LTE and NR. Logical architecture 700 may enable cooperation between and among TRPs 708. For example, cooperation may be preset within a TRP and/or across TRPs via ANC 702. In some cases, no inter-TRP interface may be needed/present.

A dynamic configuration of split logical functions may be present within logical architecture 700. The packet data convergence protocol (PDCP), radio link control (RLC), and medium access control (MAC) protocols may be adaptably placed at ANC 702 or TRP 708.

FIG. 8 illustrates an example physical architecture 800 of a distributed RAN, according to aspects of the present disclosure. Centralized core network unit (C-CU) 802 may host core network functions. C-CU 802 may be centrally deployed. C-CU 802 functionality may be offloaded (e.g., to advanced wireless services (AWS)), in an effort to handle peak capacity.

Centralized RAN unit (C-RU) 804 may host one or more ANC functions. Optionally, C-RU 804 may host core network functions locally. C-RU 804 may have distributed deployment. C-RU 804 may be closer to the network edge.

DU 806 may host one or more TRPs. DU 806 may be located at edges of the network with radio frequency (RF) functionality.

FIG. 9 is a diagram showing an example of a DL-centric subframe 900. DL-centric subframe 900 may include control portion 902. Control portion 902 may exist in the initial or beginning portion of DL-centric subframe 900. Control portion 902 may include various scheduling information and/or control information corresponding to various portions of DL-centric subframe 900. In some configurations, control portion 902 may be a physical DL control channel (PDCCH), as shown in FIG. 9. DL-centric subframe 900 may also include DL data portion 904. DL data portion 904 may sometimes be referred to as the payload of DL-centric subframe 900. DL data portion 904 may include the communication resources utilized to communicate DL data from the scheduling entity (e.g., UE or BS) to the subordinate entity (e.g., UE). In some configurations, DL data portion 904 may be a physical DL shared channel (PDSCH).

DL-centric subframe 900 may also include common UL portion 906. Common UL portion 906 may sometimes be referred to as an UL burst, a common UL burst, and/or various other suitable terms. Common UL portion 906 may include feedback information corresponding to various other portions of DL-centric subframe 900. For example, common UL portion 906 may include feedback information corresponding to control portion 902. Non-limiting examples of feedback information may include an acknowledgment (ACK) signal, a negative acknowledgment (NACK) signal, a HARQ indicator, and/or various other suitable types of information. Common UL portion 906 may include additional or alternative information, such as information pertaining to random access channel (RACH) procedures, scheduling requests (SRs), and various other suitable types of information. As illustrated in FIG. 9, the end of DL data portion 904 may be separated in time from the beginning of common UL portion 906. This time separation may sometimes be referred to as a gap, a guard period, a guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the subordinate entity) to UL communication (e.g., transmission by the subordinate entity). One of ordinary skill in the art will understand that the foregoing is merely one example of a DL-centric subframe and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

FIG. 10 is a diagram showing an example of an UL-centric subframe 1000. UL-centric subframe 1000 may include control portion 1002. Control portion 1002 may exist in the initial or beginning portion of UL-centric subframe 1000. Control portion 1002 in FIG. 10 may be similar to control portion 1002 described above with reference to FIG. 9. UL-centric subframe 1000 may also include UL data portion 1004. UL data portion 1004 may sometimes be referred to as the payload of UL-centric subframe 1000. The UL portion may refer to the communication resources utilized to communicate UL data from the subordinate entity (e.g., UE) to the scheduling entity (e.g., UE or BS). In some configurations, control portion 1002 may be a PDCCH. In some configurations, the data portion may be a physical uplink shared channel (PUSCH).

As illustrated in FIG. 10, the end of control portion 1002 may be separated in time from the beginning of UL data portion 1004. This time separation may sometimes be referred to as a gap, guard period, guard interval, and/or various other suitable terms. This separation provides time for the switch-over from DL communication (e.g., reception operation by the scheduling entity) to UL communication (e.g., transmission by the scheduling entity). UL-centric subframe 1000 may also include common UL portion 1006. Common UL portion 1006 in FIG. 10 may be similar to common UL portion 906 described above with reference to FIG. 9. Common UL portion 1006 may additionally or alternatively include information pertaining to CQI, sounding reference signals (SRSs), and various other suitable types of information. One of ordinary skill in the art will understand that the foregoing is merely one example of an UL-centric subframe and alternative structures having similar features may exist without necessarily deviating from the aspects described herein.

In some circumstances, two or more subordinate entities (e.g., UEs) may communicate with each other using sidelink signals. Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, IoT communications, mission-critical mesh, and/or various other suitable applications. Generally, a sidelink signal may refer to a signal communicated from one subordinate entity (e.g., UE1) to another subordinate entity (e.g., UE2) without relaying that communication through the scheduling entity (e.g., UE or BS), even though the scheduling entity may be utilized for scheduling and/or control purposes. In some examples, the sidelink signals may be communicated using a licensed spectrum (unlike wireless local area networks, which typically use an unlicensed spectrum).

A UE may operate in various radio resource configurations, including a configuration associated with transmitting pilots using a dedicated set of resources (e.g., a RRC dedicated state, etc.) or a configuration associated with transmitting pilots using a common set of resources (e.g., an RRC common state, etc.). When operating in the RRC dedicated state, the UE may select a dedicated set of resources for transmitting a pilot signal to a network. When operating in the RRC common state, the UE may select a common set of resources for transmitting a pilot signal to the network. In either case, a pilot signal transmitted by the UE may be received by one or more network access devices, such as an AN, a DU, or portions thereof. Each receiving network access device may be configured to receive and measure pilot signals transmitted on the common set of resources, and also receive and measure pilot signals transmitted on dedicated sets of resources allocated to the UEs for which the network access device is a member of a monitoring set of network access devices for the UE. One or more of the receiving network access devices, or a CU to which receiving network access device(s) transmit the measurements of the pilot signals, may use the measurements to identify serving cells for the UEs, or to initiate a change of serving cell for one or more of the UEs.

Example Measurement Gap Enhancements for Narrowband

As mentioned, certain systems (e.g., Release 13 or later eMTC systems), may support narrowband operation. For example, the narrowband operation may include support for communications on a 6 RB band and half-duplex operation (e.g., capability to transmit and receive, but not both simultaneously) for up to, e.g., 15 dB coverage enhancements. These systems may reserve a portion of the system bandwidth for control, which may be an MTC physical downlink control channel (MPDCCH). The MPDCCH may be transmitted in a narrowband, may use at least one subframe, and may rely on demodulation reference signal (DMRS) demodulation for decoding of the control channel. Coverage may be increased by performing repetition/bundling of signals.

Certain systems (e.g., Release 13 or later NB-IoT systems) may support narrowband Internet-of-things operation (NB-IOT). NB-IoT may use 180 kHz bandwidth. NB-IoT may offer standalone, in-band, or guard band deployment scenarios. Standalone deployment may use new bandwidth, whereas guard band deployment may be done using bandwidth typically reserved in the guard band of an existing network, such as long term evolution (LTE). In-band deployment on the other hand may use the same resource blocks in the LTE carrier of the existing LTE network. NB-IoT may offer increased coverage. NB-IoT may define a new narrowband control channel (e.g., Narrowband PDCCH (NPDCCH)), data, and references signals that fit in 1 RB.

Rel-13 and Rel-14 Cat M1 supports connected mode intra- and inter-frequency measurement during periodic gaps. Gaps are of fixed length (e.g., 6 ms) and occur every MGRP (measurement gap repetition period).

Current neighbor cell measurement is calculated using 4 CRS (common reference signal or cell-specific reference signal) symbols within 1 subframe measured on the center 6 PRBs (physical resource blocks) of the neighbor cell. Neighbor measurement accuracy may be adequate in CE (coverage enhancement) Mode A, which is designed for moderate coverage conditions.

Table 1 illustrates example gap pattern IDs.

TABLE 1 Measurement Gap Measurement Gap Repetition Period Gap Pattern Id Length (MGL, ms) (MGRP, ms) 0 6 40 1 6 80

CE Mode B is designed for more extreme coverage conditions and may be applicable for CINR<−6 dB to −18 dB. For example, for neighbor cell RSRP (reference signal received power) with 1 subframe (SF) coherent averaging (1.4 MHz system BW (bandwidth)), poor accuracy in CE Mode B with current approach exists due to insufficient coherent averaging (1 SF). There exists a need to increase coherent averaging by reusing IIR (infinite impulse response) based SE estimation when CINR (carrier interference to noise ratio)<−6 dB.

For example, RSRP measurement may use coherent averaging of raw channel estimates with single tap IIR filter (1.4 MHz system bandwidth), but with IIR based SE estimation, there is loss in RSRP accuracy in CE Mode B with current IIR coefficients, due to large bias in estimation at low SNRs (signal to noise ratios) and accuracy at −18 dB CINR may be very poor, and due to fewer CRS tones in frequency domain and insufficient IIR filtering. Improved RSRP accuracy in CE Mode B may be achieved when IIR filter coefficient is lowered (e.g., to 0.01) to allow deep filtering. Also, measurement duration may be increased (e.g., to 60 ms) to allow filter convergence. Increase measurement period at low SNR is needed coupled with deep IIR filtering to get better accuracy (e.g., lower variance). This implies longer averaging length (e.g., much greater than 6 ms).

A first problem involving measurement gaps is that they may occur concurrently with subframes that may be critical subframes. For example, during a measurement gap, subframes scheduled for the UE are skipped and not postponed (e.g., not received and/or transmitted by UE), so critical subframes like PSS (primary synchronization signal)/SSS (secondary synchronization signal)/PBCH (physical broadcast channel)/SIBs (system information block) are lost during the MGL (measurement gap length) every MGRP. Measurement gaps may affect UL (uplink) subframes as well in HD-FDD (half duplex-frequency division duplex) and TDD (time division duplex) modes. So regardless of UE's coverage mode, critical SFs could be affected due to measurement gaps resulting in performance degradation.

A second problem involving measurement gaps relates to RSRP measurement (e.g., serving cell or neighbor cell) accuracy for UEs in deep coverage. For example, for serving cell RSRP when CINR=−18 dB, measured by coherently averaging over 5 ms worth of samples collected during each 6 ms measurement gap and non-coherently averaging over 200 gaps (latency of 16 seconds with MGRP=80 ms), simulation shows that there is still ˜1 dB measurement bias. As another example, for neighbor cell RSRP measurement when CINR=−18 dB, measured by coherently averaging over 2 SF worth of samples collected during each 6 ms gap (assuming worst case availability of SFs) and non-coherently averaging over 200 gaps (latency of 16 seconds with MGRP=80 ms), simulation shows that there is ˜2 dB measurement bias.

A third problem involving measurement gaps is measurement duration in deep coverage. In one example, a UE is in the basement of a building and observes multiple cells. The UE is in CE Mode B for all cells. The UE connects on one cell but a long fade on serving cell results in better neighbor cell link quality than serving cell link. If UE does not handover (HO) to neighbor cell, a subsequent deep fade on serving cell could result in RLF (radio link failure)/OOS (out of service) followed by Fscan (frequency scan) and RRC (radio resource control) reestablishment which drains battery. For example, InitACQ on one EARFCN (E-UTRA Absolute Radio Frequency Channel Number) at −18 dB CINR may take ˜2.56 seconds with 90% detection rate in AWGN. In slow fading channel typically observed in field, the detection time is even longer. PBCH BLER may be very high at −18 dB CINR and may require many independent trials which add to overall latency. When UE measures intra-/inter-frequency neighbor cells in deep coverage (CE Mode B), 6 ms of gap length for coherent averaging may not be sufficient for an accurate RSRP measurement. Using only 6 ms of gap may lead to a highly biased neighbor cell measurement. For example, RSRP of a neighbor cell weaker than serving cell could be measured higher than the actual RSRP, which may result in incorrect handover to the weaker cell and eventually RLF/OOS followed by Fscan and RRC reestablishment on a new cell. This adversely impacts UE performance and power consumption.

Also, for neighbor measurement, there is a need to assume worst case availability of CRS SFs (since exact CRS availability is unknown). For example: SF #0, 4, 5, 9 for FDD neighbor (assuming MBSFN support) and SF #0,5 for TDD neighbor. Measurement duration per cell in CE Mode B can be high due to sparse availability. Example: Serving cell CINR dropped from −10 dB to −16 dB due to a deep fade. If Neighbor cell CINR is at −12 dB, say 15 valid subframes are required for coherent averaging to obtain an unbiased neighbor RSRP estimate. If the neighbor is on FDD band, the total measurement duration is 38 ms (=15*10/4 assuming 4 SFs, 0th, 4th, 5th, 9th SFs are valid per 10 ms). With Gap Id 1, only 5 ms (discarding tune away/tune back time of 1 ms) of measurement samples are available every MGRP=80 ms in each gap. So, 38 ms of total measurement duration spans 8 gaps which is a total measurement delay of ˜563 ms (80 ms/gap*7 gaps+3 ms of next gap) per cell. This implies UE stays in a poor cell for at least 563 ms until it can determine if it can handover (HO) to a stronger neighbor cell. Additional latency of time-to-trigger measurement event report and subsequent HO related signaling increases the overall HO delay significantly. If RLF is triggered during this time, the latency and power impact incurred due to Fscan and RRC re-establishment may be very high.

Priority-based gap scheduling may be used to address the first problem. For example, a software layer (e.g., modem software layer) maintains a lookahead scheduler to decide whether to extend a gap or not. The lookahead scheduler may maintain priorities of the subframes and measurement gaps. Priority of critical signaling is ensured, e.g., critical signals are prioritized over gap. Dynamic gap length extension may be used to address the second and third problems. For example, for CINR-based gap length scheduling, software layer schedules a gap of length ‘L’ based on serving cell CINR. For example, for neighbor RSSI-based early gap termination: during the gap, FW (firmware) may measure neighbor cell RSSI and shall decide to use all the allocated gap length or terminate the gap early and report RSRP to software layer if the neighbor cell RSSI>=Noise Floor+Δ. The number of cells to measure in each gap may be dynamically set based on the above aspects.

Example options for measurement during gaps are presented. Option 1a includes coherent averaging during the gap and either coherent averaging (e.g., resume filtering) or non-coherent averaging across 6 ms gaps. Option 1b includes non-coherent averaging of cross-correlation of consecutive CRS symbols within and across gaps. For these approaches, averaging length required may be very large resulting in big HO latency. For Option 2, gap length can be extended beyond 6 ms (e.g., to ‘L’ ms) when, for example, serving cell SINR<=−6 dB to enable long coherent averaging per gap. Tune away can be started early by ‘x’ ms, tune back can be delayed by ‘y’ ms, or both. Gap length ‘L’ can be chosen based on serving cell SINR. UE may maintain a lookup table (LUT) with mapping of serving cell SINR bin to gap length ‘L’.

FIG. 11 illustrates an example of dynamic gap length extension, e.g., for Option 2. The top half of the figure illustrates an example without gap length extension. As illustrated, there is narrowband hopping before the measurement gap and after the measurement gap. Once 5 ms of sample capture is done, offline processing begins (e.g., to calculate RSRP and RSRQ) and the measurements are available later. The bottom half of the figure illustrates an example with gap length extension. The tune away begins two subframes earlier and the tune back begins two subframes later to provide 9 ms of sample capture time. As a result of the earlier tune away and later tune back, a number of UE subframes are skipped.

Example RSRP measurement approaches include the following. In one aspect, RSRP measurement during measurement gaps (e.g., for neighbor cell or serving cell measurement) may be switched between using 1 SF coherent averaging per cell for CINR>0 dB, and longer coherent averaging per cell when CINR<0 dB. For example, for eMTC, serving cell measurements need to be made during gaps. Measurement gaps are needed for intra-/inter-frequency neighbor measurements and also serving cell measurements (measured on center 6 PRBs). Thus, both neighbor cell and serving cell measurements may be affected by measurement gaps. For long coherent averaging when CINR<0 dB, block coherent averaging may be used across SFs followed by optional non-coherent averaging (e.g., averaging length adaptively adjusted based on CINR). If serving cell gapless measurement (e.g., Rel-14 feature) is enabled, IIR (infinite impulse response) filter coefficient to filter TD (time domain) raw taps and generate CIR (used for serving cell CER (channel energy response)/RSRP estimation) may need to be optimized to work at CINR<−6 dB.

For block averaging for RSRP, coherent averaging of TD Raw Taps H[m, i] compensating for the phase ramp due to frequency error ‘ΔF’ may be performed as follows:

${{TapAvg}\left( {{\Delta\; F};m} \right)} = {\frac{1}{N}{\sum\limits_{i = 0}^{N - 1}{{H\left\lbrack {m,i} \right\rbrack}*{\exp\left( {{- j}*2*\pi*\Delta\; F*{K\lbrack i\rbrack}*0.0005} \right)}}}}$

where m∈{0, 1, 2, 3, . . . , 11} is the channel tap index;

i∈{0, 1, 2, 3, 4, 5, . . . N−1} is the counter over slot indices to be coherently averaged;

K is the slot index used for coherent averaging;

ΔF∈{0 Hz, 20 Hz, 40 Hz, 60 Hz, . . . , 180 Hz, 200 Hz, −20 Hz, −40 Hz, −60 Hz, . . . −180 Hz, −200 Hz} is a set of freq. error hypotheses divided into 20 Hz bins with max error up to +/−200 Hz;

0.0005 factor in the exponent is the slot duration of ½ ms. Thus K[i]*0.0005 is the time duration in seconds between consecutive slots with CRS availability.

Furthermore, UE can perform non-coherent averaging on successive coherent averaging blocks. One of two approaches may be used depending on CINR: Power averaging, Acorr averaging.

For power averaging, at the end of the ‘N’ slots, RSRP may be calculated as the average power across all ‘K’ CRS taps:

${RSRP\_ coh} = {\frac{1}{K}{\sum\limits_{m = 0}^{K - 1}\left\{ {{{TapAvg}\left( {{\Delta\; F};m} \right)}*{{conj}\left( {{TapAvg}\left( {{\Delta\; F};m} \right)} \right)}} \right\}}}$

Every measurement period ‘M’ slots, RSRP is calculated as the non-coherent average of RSRP_coh:

${RSRP} = {\frac{N}{M}{\sum\limits_{q = 0}^{({\frac{M}{N} - 1})}{{RSRP\_ coh}(q)}}}$

where RSRP_coh(q) is the q^(th) block of coherently averaged RSRP, and measurement duration ‘L’=M/2 subframe(s).

For Acorr averaging, at the end of the ‘N’ slots, RS autocorrelation may be calculated as the average autocorrelation across all ‘K’ CRS tap:

${RSRP\_ acorr} = {\frac{1}{K}{\sum\limits_{m = 0}^{K - 1}\left\{ {{{TapAvg}\left( {{\Delta\; F};m} \right)}*{{conj}\left( {{TapAvg}\left( {{\Delta\; F};{m - 1}} \right)} \right)}} \right\}}}$

Every measurement period ‘M’ slots, RSRP is calculated as the non-coherent average of RSRP_acorr:

${RSRP} = {\frac{N}{M}{\sum\limits_{q = 0}^{({\frac{M}{N} - 1})}{{RSRP\_ acorr}(q)}}}$

where RSRP_acorr(q) is the q^(th) block of coherently averaged RS autocorrelation, and Measurement duration ‘L’=M/2 subframe(s).

For example, power averaging may be used for CINR>−10 dB and Acorr averaging may be used for CINR<=−10 dB.

For dynamic gap length extension, option 1 may include limiting gap length L to 21 ms and non-coherently averaging across ‘G’ gaps when needed as shown in FIG. 12. Gap lengths here are for neighbor cell measurement and assumes 2 SFs available every 5 ms.

Option 2 may include using one long gap of length ‘L’ every K=ceil(L/5) gaps, and not using remaining K−1 gaps, as shown in FIG. 13. Gap lengths here are for neighbor cell measurement and assumes 2 SFs available every 5 ms.

An aspect of dynamic gap length extension is CINR-based Gap length, in which software layer schedules a gap of length ‘L’ based on serving cell CINR.

Another aspect of dynamic gap length extension is neighbor RSSI-based early gap termination. During the gap, FW, for example, measures neighbor cell RSSI and decides to use all the allocated gap length or terminate the gap early and report RSRP to the software layer if the neighbor cell RSSI>=Noise Floor+Δ. Also, FW early terminates the gap if at least 6 SFs have been coherently averaged in the gaps. This could occur for serving cell measurements during gaps since more continuously valid SFs are possible. For neighbor cell, worst case availability may need to be assumed (as mentioned, gap lengths for options 1 and 2 are for neighbor cell measurement and assumes 2 SFs available every 5 ms).

Another aspect of dynamic gap length extension is the number of cells per gap. Software layer may provide a list of neighbor cells to FW for measurement and FW may schedule all measurements sequentially and reports all measurements together in a single confirmation. For example, as shown in the table of FIG. 13, number of cells to measure per gap could be different, so the software layer may request FW confirmation on measurement per cell to enable early reselection.

As discussed, one aspect of the present disclosure involves priority based gap scheduling. If gap length extension is required, e.g., for serving cell CINR<0 dB, it is performed at least once every K=ceil(L/5) gaps per intra-/inter-frequency neighbor EARFCN in a deterministic pattern. In the remaining (K−1) gaps, UE can prioritize DL processing over measurement gap. Opportunistic gaps (outside of scheduled gap pattern) can be scheduled when Qout+Δ1<=RLM SNR<=Qin−Δ2. Here, RLM SNR may be low enough such that UE has a higher BLER (block error ratio), but not low enough for an RLF. Because the UE is expected to have higher BLER, even if subframes are lost due to the scheduled measurement gap, the loss of subframes is not at a high cost. Scheduled gap can be extended or skipped based on priority of subframes before/during/after the gap. This may need a lookahead scheduler (e.g., a simple SW C×M) to maintain priorities in the software layer. Gap extension is set to higher priority if subframe repetition is ongoing and if required number of MPDCCH/PDSCH/PUSCH repetitions ‘R’ for the CE SNR is such that Rmax−R>=L.

In an aspect, gap is not used and gap extension is postponed if, for example, critical SFs like the following are expected to occur before/during/after the scheduled gap based on the gap pattern:

PDSCH carrying mandatory SIBs during SI window

Measurement Event Report to Source eNB

HO command from Source eNB

During HO procedure

PSS/SSS Synchronization on target eNB

RACH/RAR/Msg3/Msg4 to target eNB during HO

RRC Reconfiguration Rx from target eNB during HO

RRC Reconfiguration Complete to target eNB during HO

PBCH/MIB on target cell (if sameSFN indication is not sent from source eNB)

SIB 1-BR on target cell if RRC-Reconfig message during HO does not carry it

RACH/RAR/Msg3/Msg4 due to timeAlignmentTimer expiry or PDCCH order from source eNB or data RACH

PUCCH Repetitions (CE mode A: {1, 2, 4, 8}; CE mode B: {4, 8, 16, 32})

HARQ-ACK, taking into account Rel-14 enhancement on dynamic timing relationship between PDSCH and HARQ-ACK controlled by the DCI; this adjusted timing relationship is enabled by a new optional 1-bit UE-specific RRC configuration parameter

If NB hop is pending, Option A: NB hop is prioritized over gap length extension since tune back should occur to the correct NB after gap; Option B: Tune back script is updated in the background to ensure new NB is used after gap.

Any other critical signaling like PHR/SR/BSR Tx, SRS/CQI/CSI Tx in CE Mode A, DL/UL MAC Control Element info, SPS activation/deactivation in MPDCCH and periodicity in RRC signaling

RRC signaling to be protected

[eNB→UE] RRCConnectionSetup or RRCConnectionResume

[UE→eNB] RRCConnectionSetupComplete or RRCConnectionResumeComplete

[eNB→UE] RRCConnectionReconfiguration

[UE→eNB] RRCConnectionReconfigurationComplete

[eNB→UE] SecurityModeCommand

[UE→eNB] SecurityModeCommandComplete/SecurityModeCommandFailure

[eNB→UE] UECapabilityEnquiry

[UE→eNB] UECapabilityInformation

[eNB→UE] CounterCheck

[UE→eNB] CounterCheckResponse

[eNB→UE] UElnformationRequest

[UE→eNB] UEInformationResponse

[UE→eNB] UEAssistanceInformation

Priority based gap scheduling may also take into account processing delay for RRC procedures: the delays are specified in table 11.2-1 in 36.331, by means of a value N. N=the number of 1 ms subframes from the end of reception of the E-UTRAN→UE message on the UE physical layer up to when the UE is ready for the reception of uplink grant for the UE→E-UTRAN response message with no access delay other than the TTI-alignment (e.g., excluding delays caused by scheduling, the random access procedure or physical layer synchronization). FIG. 14A further illustrates processing delay for RRC procedures.

After an RRC DL Command, the delay for UE to receive UL grant and RRC UL response can be predicted based on the table in FIG. 14B. The software layer priority scheduler could account for this delay in order to protect the UL grant reception and RRC UL response.

Another aspect of the present disclosure involves signaling enhancement. For example, UE can signal to the eNB that it needs longer gaps of duration ‘L’ every ‘K gaps, and standard enhancement may be needed. This signaling enhancement may be carried out, for example, either by signaling (L, K) to the eNB indicating that UE will use this pattern going forward, or by signaling a new gap ID corresponding to a new set of (L,K) pairs and by the network maintaining a lookup table to identify the actual gap pattern being used. Alternatively, before using a long gap, UE can signal to the network that it will use a longer gap of length ‘L’ at (SFN (system frame number) #, SF (subframe) #) pair in the future. Alternatively or additionally, UE can signal to the network that it has used a longer gap at (SFN #, SF #) in the past.

Connected mode gaps may be shared for intra- and inter-frequency measurements. Measurement gap sharing scheme may be configured by the network: New IE MeasGapSharingConfig introduced into MeasConfig. Network may configure the percentage of gaps (X) assumed for intra-frequency measurement, and the remaining percentage of gaps (1−X) may be assumed for inter-frequency measurements. Four values for X are defined. Tables 2 and 3 provide illustrations for CE Mode A and CE Mode B, respectively.

TABLE 2 Value of X (%) MeasGapSharingConfig (for CE Mode A) ‘00’ [Equal split] ‘01’ [40] ‘10’ [50] ‘11’ [60]

TABLE 3 Value of X (%) MeasGapSharingConfig (for CE Mode B) ‘00’ [Equal split] ‘01’ [50] ’10’ [75] ’11’   [87.5]

Explicit order of scheduling frequencies in the gaps may not be defined. If serving cell RSRQ is low, scheduling inter-frequency measurement before intra frequency measurements may not be optimal. Similarly, if RSRQ is high, scheduling intra-frequency measurement before inter frequency measurements may not be optimal. When multiple inter-frequency (and/or multiple intra-frequency) cells are detected, the order in which measurements are scheduled may need to be determined for fast HO.

Table 4 provides an illustration of Inter-Freq Cell Search Duration.

TABLE 4 Serving Cell CINR Range Neighbor Search Duration ‘L’ CINR >= 0 dB  1 HF −6 dB <= CINR < 0 dB  4 HF −10 dB <= CINR < −6 dB 16 HF −15 dB <= CINR < −10 dB 32 HF CINR < −15 dB 64 HF

For example, in one scheduling approach, if serving cell RSRQ<[−18 dB]: if intra-frequency search is not run in the last 5 seconds: first run intra-frequency search in one-shot; then schedule intra-frequency measurements on set of cells with SSS-SNR>=[−6 dB]; then schedule intra-frequency measurements on set of cells with SSS-SNR<[−6 dB]. For all intra-frequency cells, measurements in each set may be scheduled in decreasing order of SSS-SNR.

If RSRQ>=[−18 dB], for example, if inter-frequency search on an EARFCN is not run in the last 5 seconds, inter-frequency search may be run first. Then inter-frequency measurements on set of cells with SSS-SNR>=[−6 dB] may be scheduled. Then inter-frequency measurements on set of cells with SSS-SNR<[−6 dB] may be scheduled. Similarly, for all inter-frequency cells, measurements in each set in decreasing order of SSS-SNR may be scheduled.

The provided techniques may provide fast measurement and handover (e.g., especially in CE Mode B) and offer significant latency reduction.

FIG. 15 is a flow diagram illustrating example operations 1500 for UE behavior, according to aspects described herein. Operations 1500 may be performed, for example, by a UE (e.g., UE 120) which may be a low cost, NB, and/or IoT device, and/or a device that's in coverage enhancement. Operations 1500 may begin, at 1502, by determining a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap. At 1504, the UE adjusts the measurement gap based on at least one criterion. In an aspect, subframes scheduled for the UE are not received during the measure gap, and adjusting the measurement gap comprises at least one of: extending the measurement gap, comprising extending a length of time of the measurement gap; skipping the measurement gap; terminating the measurement gap early; postponing the measurement gap; or scheduling a new measurement gap outside the scheduled occurrence of the measurement gap. In an aspect, the at least one criterion is based, at least in part, on a priority of subframes expected to conflict with the measurement gap. In an aspect, the UE signals to a base station information regarding the extended measurement gap. In an aspect, the information indicates an extended length of time of the measurement gap for the UE and a frequency of occurrence of the extended measurement gap among a number of measurement gaps. In an aspect, the information comprises a gap identification (ID) corresponding to a set of information indicating an extended length of time of the measurement gap for the UE and a frequency of occurrence of the extended measurement gap among a number of measurement gaps, and wherein a lookup table (LUT) matching the gap ID and the corresponding set of information is available to the base station. In an aspect, the UE, before the extended measurement gap, signals the base station that it will use an extended measurement gap of length L at an indicated system frame number (SFN) and subframe number (SN). In an aspect, the UE, after the extended measurement gap, signals the base station that it used an extended measurement gap of length L at an indicated system frame number (SFN) and subframe number (SN). In an aspect, extending the measurement gap comprises scheduling a measurement gap of length L based at least in part on a metric. In an aspect, L comprises the length of time for the scheduled measurement gap or a number of subframes for the scheduled measurement gap. In an aspect, the metric comprises serving cell carrier-to-interference-and-noise-ratio (CINR) or signal-to-interference-and-noise-ratio (SINR). In an aspect, the method comprises maintaining a look-up table (LUT) with mapping of serving cell CINR or SINR to measurement gap length L. In an aspect, extending the measurement gap further comprises at least one of: starting tune-away early, or delaying tune-back. In an aspect, the method further comprises setting an upper limit for L and non-coherently averaging across G gaps, based at least in part on a signal strength of a serving cell of the UE or a signal strength of a neighbor cell, wherein G indicates a number of gaps. In an aspect, the signal strength of the serving cell comprises CINR and the signal strength of the neighbor cell comprises received signal strength indicator (RSSI). In an aspect, the method further comprises scheduling the extended measurement gap of length L every K gaps, based at least in part on a signal strength of a serving cell of the UE or a signal strength of a neighbor cell, wherein K indicates a number of measurement gaps. In an aspect, K=ceil(L/5) gaps, and further comprising skipping the remaining K−1 measurement gaps. In an aspect, the signal strength of the serving cell comprises CINR and the signal strength of the neighbor cell comprises received signal strength indicator (RSSI). In an aspect, the method further comprises: measuring neighbor cell signal strength during the extended measurement gap; and terminating the extended measurement gap early based at least in part on comparing the measured neighbor cell signal strength with a threshold. In an aspect, the measured neighbor cell signal strength comprises received signal strength indicator (RSSI). In an aspect, the method comprises reporting a signal strength measurement. In an aspect, the signal strength measurement comprises reference signal received power (RSRP). In an aspect, the method further comprises dynamically setting a number of cells to measure in each measurement gap. In an aspect, the method further comprises selecting between coherent averaging for one subframe per cell using an unextended measurement gap and longer coherent averaging across subframes per cell using the extended measurement gap, based at least in part on comparing a CINR of a serving cell of the UE with a threshold. In an aspect, selecting coherent averaging is based at least in part on the CINR being greater than the threshold, and selecting longer coherent averaging is based at least in part on the CINR being less than the threshold. In an aspect, the longer coherent averaging across subframes is selected, comprising applying block coherent averaging across subframes followed by non-coherent averaging the longer coherent averaging across subframes is selected, comprising applying block coherent averaging across subframes followed by non-coherent averaging. In an aspect, the non-coherent averaging comprises non-coherent averaging on successive coherent averaging blocks, and wherein a type of non-coherent averaging is selected based at least part on CINR of the serving cell. In an aspect, a first type of non-coherent averaging is selected when the CINR is above a threshold, and a second type of non-coherent averaging is selected when the CINR is below or equal a threshold. In an aspect, the method further comprises performing the first type of non-coherent averaging, comprising: calculating RSRP as an average power across all K common reference signal (CRS) taps at end of N slots, wherein K comprises a slot index used for coherent averaging; and calculating RSRP as a non-coherent average of the qth block of coherently averaged RSRP of M slots of every measurement period, wherein L, the length of time of the extended measurement gap, includes M/2 subframes. In an aspect, the method further comprises performing the second type of non-coherent averaging, comprising: calculating reference signal (RS) autocorrelation as an average autocorrelation across all K CRS taps, wherein K comprises a slot index used for coherent averaging at end of N slots; and calculating RSRP as a non-coherent average of the qth block of coherently averaged RS autocorrelation of M slots every measurement period, wherein L, the length of time of the extended measurement gap, includes M/2 subframes. In an aspect, the method further comprises performing downlink (DL) operations during remaining measurement gaps that are not extended. In an aspect, scheduling a new measurement gap outside the scheduled occurrence of the measurement gap is based at least in part on comparison of downlink signal quality with at least one threshold. In an aspect, the downlink signal quality comprises signal-noise-ratio (SNR) calculated as part of radio link monitoring (RLM) procedure and the at least one threshold comprises Qout and Qin used in the RLM procedure. In an aspect, the method further comprises maintaining priorities of subframes and measurement gaps. In an aspect, the method further comprises increasing a priority of an extended measurement gap based, at least in part, on ongoing subframe repetition and a number of repetitions for decoding a channel is below a threshold. In an aspect, the channel comprises at least one of a control channel or data channel, further comprising setting the priority higher if the threshold meets the criteria that the difference of a maximum number of allowed repetitions and the number of repetitions needed for decoding is greater than or equal to a number of subframes in the extended measurement gap. In an aspect, the method further comprises scheduling the extended measurement during a period comprising the difference between the maximum number of allowed repetitions and the number of repetitions needed for decoding. In an aspect, the subframes expected to conflict with the measurement gap comprises subframes that begin before, occur during, or end after the scheduled measurement gap. In an aspect, the UE supports coverage enhancement (CE) mode. In an aspect, the UE supports narrowband operation. In an aspect, the UE supports enhanced machine type communications (eMTC). In an aspect, the UE supports narrowband internet of things (NB-IoT). In an aspect, a base station receives information from a UE regarding an adjusted measurement gap. In an aspect, the information indicates an extended length of time of the measurement gap the UE needs and a frequency of occurrence of the extended measurement gap among all measurement gaps. In an aspect, the information comprises a gap identification (ID) corresponding to a set of information indicating an extended length of time of the measurement gap the UE needs and a frequency of occurrence of the extended measurement gap among all measurement gaps, and wherein a lookup table (LUT) matching the gap ID and the corresponding set of information is available to the base station. In an aspect, the base station receives the information, before the extended measurement gap, from the UE that the UE will use an extended measurement gap of length L at an indicated system frame number (SFN) and subframe number (SN). In an aspect, the base station receives the information, after the extended measurement gap, from the UE that the UE used an extended measurement gap of length L at an indicated system frame number (SFN) and subframe number (SN).

As mentioned, adjusting the measurement gap may comprise at least one of: extending the measurement gap, comprising extending a length of time of the measurement gap; skipping the measurement gap; terminating the measurement gap early; postponing the measurement gap; or scheduling a new measurement gap outside the scheduled occurrence of the measurement gap. The at least one criterion on which adjusting the measurement gap may be based, at least in part, on a priority of subframes expected to conflict with the measurement gap. The UE may signal to a base station information regarding the extended measurement gap. Extending the measurement gap may comprise scheduling a measurement gap of length L based at least in part on a metric. L may comprise the length of time for the scheduled measurement gap or a number of subframes for the scheduled measurement gap, and the metric may comprise cell carrier-to-interference-and-noise-ratio (CINR) or signal-to-interference-and-noise-ratio (SINR). A base station may receive information from the UE regarding the adjusted measurement gap. The information may indicate an extended length of time of the measurement gap the UE needs and a frequency of occurrence of the extended measurement gap among all measurement gaps.

As used herein, the term “identifying” encompasses a wide variety of actions. For example, “identifying” may include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “identifying” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “identifying” may include resolving, selecting, choosing, establishing and the like.

Moreover, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from the context, the phrase, for example, “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, for example the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. As used herein, reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” For example, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form. Unless specifically stated otherwise, the term “some” refers to one or more. A phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination with multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c). As used herein, including in the claims, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

In some cases, rather than actually communicating a frame, a device may have an interface to communicate a frame for transmission or reception. For example, a processor may output a frame, via a bus interface, to an RF front end for transmission. Similarly, rather than actually receiving a frame, a device may have an interface to obtain a frame received from another device. For example, a processor may obtain (or receive) a frame, via a bus interface, from an RF front end for transmission.

The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims.

The various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in Figures, those operations may be performed by any suitable corresponding counterpart means-plus-function components.

For example, means for determining, means for adjusting, means for extending, means for skipping, means for terminating, means for postponing, means for scheduling, means for maintaining, means for indicating, means for setting, means for measuring, means for selecting, means for applying, means for calculating, means for performing, means for transmitting, means for receiving, means for sending, means for signaling, means for requesting, and/or means for deriving may include one or more processors, transmitters, receivers, antennas, and/or other elements of the user equipment 120 and/or the base station 110 illustrated in FIG. 2.

Those of skill in the art would understand that information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or combinations thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as hardware, software, or combinations thereof. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. One or more aforementioned devices or processors may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination thereof. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, phase change memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

In one or more exemplary designs, the functions described may be implemented in hardware, software, or combinations thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD/DVD or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. 

What is claimed is:
 1. A method of wireless communication for a user equipment (UE), comprising: determining a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap; and adjusting the measurement gap based on at least one criterion, wherein adjusting the measurement gap comprises scheduling a new measurement gap outside the scheduled occurrence of the measurement gap based at least in part on comparison of downlink signal quality with at least one threshold, and wherein the at least one criterion is based, at least in part, on a priority of subframes expected to conflict with the measurement gap.
 2. The method of claim 1, wherein the UE signals to a base station information regarding an extended measurement gap.
 3. The method of claim 2, wherein the information indicates an extended length of time of the measurement gap for the UE and a frequency of occurrence of the extended measurement gap among a number of measurement gaps.
 4. The method of claim 2, wherein the UE, before the extended measurement gap, signals the base station that the UE will use an extended measurement gap of length L at an indicated system frame number (SFN) and subframe number (SN).
 5. The method of claim 2, wherein the UE, after the extended measurement gap, signals the base station that the UE used an extended measurement gap of length L at an indicated system frame number (SFN) and subframe number (SN).
 6. The method of claim 1, wherein adjusting the measurement gap further comprises extending the measurement gap, the extending the measurement gap comprising scheduling a measurement gap of length L based at least in part on a metric.
 7. The method of claim 6, wherein L comprises the length of time for the scheduled measurement gap or a number of subframes for the scheduled measurement gap.
 8. The method of claim 6, wherein the metric comprises serving cell carrier-to-interference-and-noise-ratio (CINR) or signal-to-interference-and-noise-ratio (SINR).
 9. The method of claim 6, further comprising: measuring neighbor cell signal strength during the extended measurement gap; and terminating the extended measurement gap early based at least in part on comparing the measured neighbor cell signal strength with a threshold.
 10. The method of claim 6, further comprising dynamically setting a number of cells to measure in each measurement gap.
 11. The method of claim 6, further comprising performing downlink (DL) processing operations during remaining measurement gaps that are not extended.
 12. An apparatus for wireless communication at a user equipment (UE), comprising: at least one processor; and a memory coupled to the at least one processor, the memory comprising instructions executable by the at least one processor to cause the apparatus to: determine a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap, and adjust the measurement gap based on at least one criterion, wherein adjusting the measurement gap comprises scheduling a new measurement gap outside the scheduled occurrence of the measurement gap based at least in part on comparison of downlink signal quality with at least one threshold, and wherein the at least one criterion is based, at least in part, on a priority of subframes expected to conflict with the measurement gap.
 13. The apparatus of claim 12, wherein the UE signals to a base station information regarding an extended measurement gap.
 14. The apparatus of claim 13, wherein the information indicates an extended length of time of the measurement gap for the UE and a frequency of occurrence of the extended measurement gap among a number of measurement gaps.
 15. The apparatus of claim 13, wherein the memory further comprises instructions executable by the at least one processor to cause the apparatus to: before the extended measurement gap, signal the base station that the UE will use an extended measurement gap of length L at an indicated system frame number (SFN) and subframe number (SN).
 16. The apparatus of claim 13, wherein the memory further comprises instructions executable by the at least one processor to cause the apparatus to: after the extended measurement gap, signal the base station that the UE used an extended measurement gap of length L at an indicated system frame number (SFN) and subframe number (SN).
 17. The apparatus of claim 12, wherein the adjusting the measurement gap further comprises extending the measurement gap, wherein the extending the measurement gap comprises scheduling a measurement gap of length L based at least in part on a metric.
 18. The apparatus of claim 17, wherein L comprises the length of time for the scheduled measurement gap or a number of subframes for the scheduled measurement gap.
 19. The apparatus of claim 17, wherein the metric comprises serving cell carrier-to-interference-and-noise-ratio (CINR) or signal-to-interference-and-noise-ratio (SINR).
 20. The apparatus of claim 17, wherein the memory further comprises instructions executable by the at least one processor to cause the apparatus to: measure neighbor cell signal strength during the extended measurement gap; and terminate the extended measurement gap early based at least in part on comparing the measured neighbor cell signal strength with a threshold.
 21. The apparatus of claim 17, wherein the memory further comprises instructions executable by the at least one processor to cause the apparatus to dynamically set a number of cells to measure in each measurement gap.
 22. The apparatus of claim 17, wherein the memory further comprises instructions executable by the at least one processor to cause the apparatus to perform downlink (DL) processing operations during remaining measurement gaps that are not extended.
 23. An apparatus for wireless communication at a user equipment (UE), comprising: means for determining a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap; and means for adjusting the measurement gap based on at least one criterion, wherein the means for adjusting the measurement gap comprises means for scheduling a new measurement gap outside the scheduled occurrence of the measurement gap based at least in part on comparison of downlink signal quality with at least one threshold, and wherein the at least one criterion is based, at least in part, on a priority of subframes expected to conflict with the measurement gap.
 24. A non-transitory computer-readable medium for wireless communication at a user equipment (UE), the computer-readable medium comprising code, when executed by at least one processor, the code causes the at least one processor to: determine a scheduled occurrence of a measurement gap, wherein the UE measures neighbor cell signal strength during the measurement gap, and adjust the measurement gap based on at least one criterion, wherein adjusting the measurement gap comprises scheduling a new measurement gap outside the scheduled occurrence of the measurement gap based at least in part on comparison of downlink signal quality with at least one threshold, and wherein the at least one criterion is based, at least in part, on a priority of subframes expected to conflict with the measurement gap. 